1. Technical Field
The present invention relates to a control system including a controller which executes a user program periodically, and more particularly, to a control system which is connected to a database system.
2. Related Art
Machinery and equipment used in many production sites are typically controlled by a control system including, as a main component, a controller such as a programmable logic controller (hereinbelow, also called “PLC”). A controller such as a PLC is used for a control or the like of an automatic machine in a factory or the like, has a plurality of input/output functions, for example, sequentially reads values which are output from sensors and the like and holds the values.
In recent years, a PLC which is connected to a database system is known. A PLC stores data held in the PLC into a database system. It facilitates sharing of data among information processing apparatuses connected to a database, collection of various pieces of data, counting, analysis, and the like of the data. For example, Japanese Unexamined Patent Publication No. 2012-108642 discloses a PLC having the function of transmitting a SQL process group including a plurality of SQL statements to access a database to the database.